Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151255 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 855 AM EDT WED OCT 15 2014 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO PUSH ACROSS THE EASTERN SEABOARD INTO THE AFTERNOON HOURS TODAY. THE BOUNDARY WILL GRADUALLY DRIFT ACROSS THE LOWLANDS AND COASTAL AREAS LATER THIS EVENING...AND OFF THE COAST TONIGHT. THE PARENT UPPER-LEVEL LOW WILL PERSIST OVER THE AREA INTO EARLY FRIDAY MORNING. A BRIEF REPRIEVE TAKES SHAPE BEFORE ANOTHER UPPER TROUGH SLIDES COOLER AND DRIER AIR INTO THE REGION TO BEGIN THE UPCOMING WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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UPDATE...ADDED TO THE FLOOD WATCH FROM FREDERICK TO WARRENTON TO FREDERICKSBURG...AS THATS WHERE THE HVY RAFL IS OCCURRING ATTM. FWD MVMT HAS SLOWED. QPF WIDESPREAD 1 TO 2 INCHES...W/ HIER AMTS XPCTD. PREVIOUS DISCUSSION... COMPLEX LOW PRESSURE SYSTEM WILL IMPACT THE MIDDLE ATLANTIC REGION TODAY. CENTER OF THE LARGE UPPER CUTOFF LOW CENTERED OVER THE MIDWEST WILL GRADUALLY LIFT EASTWARD TODAY. AN ABUNDANT FETCH OF RICH MOISTURE SEEN ON ENHANCED WATER VAPOR IMAGERY WILL FEED NORTHWARD INTO THE MIDDLE ATLANTIC REGION TODAY. PWATS RUNNING IN THE 1.5 TO 2.0 RANGE WILL BE PRIME FOR HEAVY RAINFALL TODAY. A POTENT BAND OF HEAVY SHOWERS AND EMBEDDED THUNDERSTORMS WILL TRAIN ACROSS THE POTOMAC HIGHLANDS...SHENANDOAH VALLEY AND I-81 CORRIDOR THIS MORNING THEN EASTWARD ACROSS THE REMAINDER OF THE FORECAST AREA INCLUDING THE WASHINGTON DC AND BALTIMORE METRO AREAS THIS AFTERNOON. SHOWERS AHEAD OF THE MAIN BAND WILL MOISTEN THE SOILS AHEAD OF THE MAIN ACTION. WILL LEAVE FLASH FLOOD WATCH CONFIGURATION THE SAME WITH THE THREAT OCCURRING THIS MORNING UNTIL MIDDAY. DECIDED TO ISSUE A FLOOD WATCH FOR THE DC AND BALTIMORE METRO AREAS FROM 14-00Z. EXPECTING 1-3 INCHES OF RAINFALL WITH LOCALLY HIGHER AMOUNTS POSSIBLE. NOT EXPECTING FLASH FLOODING BUT MORE URBAN AND LOW LYING FLOODING FOR AREAS ESPECIALLY PRONE TO IT. IN ADDITION TO THE THREAT FOR HEAVY RAINFALL AND FLOODING...THERE REMAINS MARGINAL INSTABILITY PARAMETERS AND STRONG WINDS OFF THE DECK. THIS WILL LIKELY LEAD TO THE POTENTIAL FOR SOME DAMAGING WIND GUSTS ESPECIALLY WHERE STRONGER STORMS DEVELOP. WILL CONTINUE TO HIGHLIGHT IN THE HWO. RAIN WILL END OVER EASTERN SECTIONS LATER THIS EVENING BUT CLOUD COVER WILL REMAIN IN PLACE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... THE BULK OF THE RAINFALL WILL TAPER OFF THIS EVENING/EARLY TONIGHT ALTHOUGH A FEW SHOWERS CANNOT BE RULED OUT GIVEN THE UPPER LOW TO THE WEST. AREAS OF FOG WILL LIKELY DEVELOP GIVEN THE MOIST SOIL CONDITIONS. OVERNIGHT LOWS IN THE 40S TO 50S WILL BE COMMON. UPPER LOW WILL BEGIN TO GRADUALLY PULL AWAY TO THE NORTH ON THURSDAY. A FEW SHOWERS COULD STILL OCCUR ESPECIALLY OVER WESTERN SECTIONS. HIGHS IN THE 60S AND 70S EXPECTED. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... AFTER HANGING AROUND FOR A COUPLE OF DAYS...AS CUT-OFF UPPER LOWS TYPICALLY DO - ONE LAST SWIPE OF A BACK-END UPPER VORT AND THE SYSTEM WILL MAKE A FAIRLY QUICK EXIT TO THE NE. FROM LATE THU INTO THE EARLY MRNG HRS FRI...THIS LAST BURST OF ENERGY WILL EFFECTIVELY END PRECIP ACROSS THE REGION AND START CLEARING OUT SKIES OVERNIGHT. ALWAYS A CHALLENGE IN TERMS OF EXACT TIMING/MOVEMENT...MED RANGE MODELS APPEAR TO HAVE A GOOD HANDLE ON THE EXITING FEATURE. THE EURO STILL LAGGING SLIGHTLY W/ THE TIMING...AS IT HAS BEEN COMPARED TO THE GFS/NAM OVER THE PAST SEVERAL CYCLES. TAPERED OFF POPS A BIT MORE QUICKLY HEADING INTO THE OVERNIGHT HRS - OUTSIDE OF THE MTNS... WHERE CLOUD COVER WILL ALSO REMAIN NEAR-OVC WELL INTO EARLY FRI. HUMIDITY LEVELS WILL BE LOWER HEADING INTO THE END OF THE CURRENT WEEK...BUT NOT SUBSTANTIALLY - INDICATIVE OF VERY LITTLE ACTUAL AIRMASS CHANGE EVEN W/ THE ARRIVAL/PASSAGE OF SUCH A POTENT SYSTEM. WITH THE EXIT OF THE UPPER SYSTEM INTO FRI...NOT ONLY DEWPOINTS BUT TEMPS WILL BE ABLE TO REBOUND FAIRLY WELL AS WINDS AGAIN SWITCH BACK TO A MORE S-SWLY FETCH. HIGHS WILL BARELY REACH THE U60S/L70S INTO THE WEEKEND BUT STILL FAIRLY WARM CONSIDERING THE TYPE OF POTENT SYSTEM THAT MOVED ACROSS THE REGION. AN ANOMALOUS AND NEAR PRECIP-LESS CLIPPER FEATURE WILL BE LINKING-UP INTO THE WRN SIDE OF THE EXITING UPPER LOW ON FRI. IN AN INTERESTING PHYSICAL DISPLAY OF TWO SEPARATE LOW INTERACTING W/ EACH OTHER...THE SMALLER LOW SLIDING IN FROM THE WEST WILL BE ABSORBED INTO THE LARGER/SLOWER SYSTEM OVER THE GREAT LAKES - BUT THEN GET SWING BACK DOWN ACROSS NEW ENGLAND/MID-ATLC AS A SHARP TROUGH AXIS. THIS IS THE FEATURE THAT WILL BRING BACK A TASTE OF FALL...W/ DEWPOINTS DROPPING DOWN INTO THE 30S/40S - ALLOWING DAYTIME HIGHS AND OVERNIGHT LOWS TO MAKE SIMILAR DROPS HEADING INTO EARLY NEXT WEEK. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/... SUB VFR CIGS AND VSBYS EXPECTED TODAY INTO TONIGHT. HEAVY RAINFALL...ISOLATED DAMAGING WINDS EXPECTED TODAY AT ALL TERMINAL SITES. AREAS OF FOG WILL DEVELOP OVERNIGHT. CONDITIONS WILL IMPROVE ON THURSDAY. THE SLOW-MOVING AND PERSISTENT UPPER LOW WILL ACTUALLY MAKE A QUICK EXIT BY EARLY FRI...ALLOWING A BRIEF ARRIVAL OF HIGH PRESSURE ON FRI AND INTO THE WEEKEND. BREEZY WLY WINDS ABOUT THE ONLY WX-HAZARD OF NOTE SAT AND SUN. A FAIRLY DRY FORECAST INTO EARLY NEXT WEEK...AS MORE FALL-LIKE WX RETURNS. && .MARINE... WIDESPREAD SCA CONDITIONS EXPECTED TODAY. BAND OF SHOWERS AND STORMS MAY MIX DOWN STRONGER WINDS ALOFT LEADING TO SPECIAL MARINE WARNINGS THIS AFTERNOON AND EVENING. WINDS WILL FALL BELOW SCA ON THURSDAY. THE EXIT OF AN UPPER LOW BY EARLY FRI WILL MARK THE BEGINNING OF A QUIET COUPLE OF DAYS OVER THE WATERS TO CLOSE OUT THE WEEK. A LIGHT S-SW WIND OVER THE BAY ON FRI AFTN. A SECONDARY WAVE OF DRY BUT BREEZY LOW PRESSURE WILL CAUSE GUSTY WINDS ON SAT AND SUN AFTNS. SMALL CRAFT POTENTIAL EACH DAY. HIGH PRESSURE EXPECTED TO BUILD IN BEHIND THIS WAVE TO START THE WORK WEEK. && .HYDROLOGY...
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HVY RAFL STRETCHING FROM FREDERICK TO FREDERICKSBURG ATTM...W/ LIGHTER BUT STDY AMTS WEST TO THE APLCNS. OBSVD REPORTS OF AN INCH OR TWO...WITH AREAS UP TO 3 INCHES. MOST OF THE RAINFALL OUT OF THE HEADWATERS. MAY HV SMALL STREAM ISSUES AS WELL AS ON RAPID RISING WATERWAYS AND URBAN AREAS. FLASH FLOOD WATCH SW TIL NOON...AND FLOOD WATCH UNDER CURRENT ACTIVITY EWD TO INCL DC METRO TIL 8PM.
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&& .TIDES/COASTAL FLOODING... POSITIVE TIDAL ANOMALIES STILL HOVERING WITHIN A TENTH INCH OF 1.0 FT. SOUTHEASTERLY FLOW CONTINUES TO BANK 15-25KT BREEZES INTO THE WRN SHORES OF THE MD BAY/TP RVR. BECAUSE OF THIS STEADY FLOW... ANOMALIES WILL CONTINUE TO INCREASE BUT ALSO AT A SLOW-STEADY RATE. THE DAYTIME HIGH TIDE CYCLE IS THE LESSER DIURNAL TIDE. SOUTH OR SOUTHEAST FLOW WILL BE THE STRONGEST IN THIS TIME...BUT MOST PLACES WILL REQUIRE AN EXTRA 0.5 TO 0.8 FT ANOMALY. HOWEVER... BASED ON CURRENT DEPARTURES...ANNAPOLIS WILL EXCEED MINOR CRITERIA BY SEVERAL INCHES. A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR ANNE ARUNDEL CNTY TDA. HIGH TIDE LATE TONIGHT IS THE PREFERRED AND MORE SOUTH WINDS ARE EXPECTED AFTER THE FRONTAL BOUNDARY...SO ONGOING ELEVATED WATERS COULD RESULT IN SOME MINOR COASTAL FLOODING. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR DCZ001. MD...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR MDZ004-009>011-013- 014. COASTAL FLOOD ADVISORY UNTIL 3 PM EDT THIS AFTERNOON FOR MDZ014. VA...FLASH FLOOD WATCH UNTIL NOON EDT TODAY FOR VAZ025>027-029-030- 036>040-503-504. FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR VAZ042-050>056-501- 502. WV...FLASH FLOOD WATCH UNTIL NOON EDT TODAY FOR WVZ055-501-502-505- 506. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530>532-539>542. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ535- 536-538. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ533- 534-537-543.
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&& $$ SYNOPSIS...GMS NEAR TERM...HTS/KRW/BAJ SHORT TERM...KRW LONG TERM...GMS AVIATION...GMS/KRW MARINE...GMS/KRW HYDROLOGY...HTS TIDES/COASTAL FLOODING...HTS/JE

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